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Marijuana Less Likely To Elevate Vehicle Crash Risk As Compared To Other Substances


drunk driving alcohol marijuana studyNew York, NY: The presence of various controlled substances in blood is associated with an increased risk of fatal crash involvement, according to data published online in the journal Accident Analysis and Prevention.

Investigators at Columbia University conducted a case-control study to assess the association between drug use and fatal crash risk. Of the substances identified by researchers, authors reported that depressants were most likely to be associated with crash risk (estimated odds ratio = 4.83). Estimated odds ratios for other specific drug categories were 3.57 for stimulants, 3.41 for polydrug use (excluding alcohol), and 3.03 for narcotics. Marijuana (1.83) possessed the lowest odds ratios of the substances identified.

The odds ratio for cannabis is similar to that reported in a 2012 meta-analysis of 66 separate studies which estimated that cannabis was associated with a nominally increased risk of accident (estimated odds ratio = 1.25). In that study, anti-histamines (1.12) and penicillin (1.12) were associated with comparable odds to cannabis.

Previous studies assessing fatal crash risks have reported far higher odds ratios for alcohol. According to a 2004 study published in the journal Epidemiology, drivers who self-reported consuming two or more alcoholic drinks in a six-hour period prior to driving were nearly eight times more likely to suffer a car crash-related injury compared to non-drinkers.

While Columbia researchers did not assess the risk of alcohol consumption alone, they did report that the use of alcohol in combination with controlled substances increased subjects’ risk of fatal accident more than 20-fold.

For more information, please contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, “Drug use and fatal motor vehicle crashes: A case-control study,” appears in Accident Analysis and Prevention.

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Johnny Green


  1. I’ve been looking for a stop sign that turns green for ages. They can put a woman on the moon, but they can’t get a stop sign to turn green. I mean, stop lights turn green. I don’t know why stop signs have to be so, what’s the word for it… difficult. Anyway, EVERYTHING should be green ALL the time. The end.

  2. It’s hard for me to understand because I’ve never had that effect. Of course, not much can make me sleepy. I was wondering, are you a lightweight in other pharmaceutical areas? (Not to say that being a lightweight is a bad thing, jeez, I wish I could say that…) Or is that too personal?

  3. throwaway1133211 on

    I’ll chime in on this as well. Benadryl DESTROYS me. I only take it if I plan on passing out soon because it makes me extremely drowsy.

  4. Statistics are great, but they never tell the complete story. For instance, I know people who’s driving is impaired by a factor of 2 when they take an antihistamine. (People take Benadryl to help them sleep, really.)

    I never heard the joke about the stop signs. Hilarious.

  5. Interesting. I wasn’t aware of these studies. Cannabis use puts you at risk of an accident at about the same rate as penicillin and antihistamines — neither of which are tested for road-side by the police (or by employers, for that matter).

    Maybe there is a lot of credence to the old joke about drunks running stop signs while stoners sit there waiting for the stop sign to turn green. Or rather, what I personally think is the case, people who use cannabis *know* they’re impaired and can’t drive, more often than not. States with medical cannabis laws enacted, on average, see a 9% drop in DUIs and DUI fatalities.

    Other substances — alcohol, especially — are infamous of robbing people of their better judgement who then drive when they should not.

    Sure would be SUPER if they would reschedule cannabis to Schedule III so that we could study the effects and SEE WHAT IS ACTUALLY THE CASE. Am I glad medical cannabis states are having fewer traffic deaths? Absolutely. But that’s not enough. I’d like to know *why* — are they simply choosing to not drive when they shouldn’t, are they driving *anyway* and still driving cautiously, is there a third variable we haven’t accounted for like the 5% drop in beer sales? WE DO NOT KNOW.

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